Enhanced ablation and mapping catheter and method for treating atrial fibrillation

ABSTRACT

A catheter for ablating tissue is provided. The catheter comprises an elongated generally-tubular catheter body having proximal and distal ends. An electrode assembly is provided at the distal end of the catheter body. The electrode assembly including a porous electrode arrangement that is generally transverse to the catheter body. The porous electrode arrangement comprises one or more electrodes electrically connected to a suitable energy source and a porous sleeve mounted in surrounding relation to the one or more electrodes and defining an open space between the porous sleeve and the one more electrodes. One or more irrigation openings fluidly connect the open space to a lumen extending through the catheter through which fluid can pass. In use, fluid passes through the lumen in the catheter, through the one or more irrigation openings, into the open space and through the porous sleeve.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of U.S. patent application Ser. No.10/622,621, entitled ENHANCED ABLATION AND MAPPING CATHETER AND METHODFOR TREATING ATRIAL FIBRILLATION, filed Jul. 18, 2003, the entirecontents of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an improved steerable electrodecatheter having an irrigated ablation electrode that is particularlyuseful for treating atrial fibrillation.

BACKGROUND OF THE INVENTION

Atrial fibrillation is a common sustained cardiac arrhythmia and a majorcause of stroke. This condition is perpetuated by reentrant waveletspropagating in an abnormal atrial-tissue substrate. Various approacheshave been developed to interrupt wavelets, including surgical orcatheter-mediated atriotomy. It is believed that to treat atrialfibrillation by radio-frequency ablation using a catheter, continuouslinear lesions must be formed to segment the heart tissue. By segmentingthe heart tissue, no electrical activity can be transmitted from onesegment to another. Preferably, the segments are made too small to beable to sustain the fibrillatory process. A preferred technique fortreating atrial fibrillation by radio-frequency ablation would be a“branding iron” approach, where a relatively long electrode can be heldstationary in good contact with the heart wall while ablation iscompleted. In this way, a continuous transmural burn may be effected.

U.S. Pat. No. 5,800,428 to Nelson et al. discloses a radio frequencyablation catheter system having a flexible, tubular electrode forcreating a continuous linear lesion. The tubular electrode isselectively extendable from the distal end of the catheter. The catheterfurther comprises mechanisms for remotely manipulating and extending theelectrode. However, having an extendable electrode house in the catheterprovides less degrees of freedom with respect to the shape, size andlength of the tubular electrode. Moreover, the physician has to dealwith additional moving and manipulatable parts, adding complexity to theprocedure. Further, a retractable electrode can cause contaminationbecause blood or coagulate on the electrode can be pulled into andentrapped inside the catheter. The entrapped coagulate can also affectthe ability of the electrode to be further extended and retracted.Accordingly, it would be desirable to provide a catheter design havingan electrode for creating linear lesions that overcomes these drawbacks.

U.S. patent application Ser. No. 10/199,525, entitled “Atrial AblationCatheter and Method for Treating Atrial Fibrillation” discloses acatheter having an ablation assembly bent relative to the catheter bodyand comprising a generally-straight non-retractable tubular electrodeformed of a material having shape-memory having at least one irrigationport through which fluid can pass from the inside to the outside of theelectrode. However, in order to create lesions that are sufficientlydeep to treat arrhythmias, a relatively high level of radio frequencypower is often needed, which can result in coagulum formation and tissuecharring. The irrigation ports in the tubular electrode described inU.S. patent application Ser. No. 10/199,525 permit the use of coolingfluid to reduce coagulum formation and tissue charring. However, if theirrigation is not efficiently delivered to the tissue being treated,local hot spots can develop at the tissue/electrode interface.Accordingly, a need exists for an improved catheter containing anelongated electrode that can provide more efficient cooling duringablation.

SUMMARY OF THE INVENTION

The invention is directed to an improved catheter and method forablating linear lesions while ensuring delivery of cooling saline to thetissue being ablated. In one embodiment, the invention is directed to acatheter comprising an elongated generally-tubular catheter body havingproximal and distal ends. An electrode assembly is provided at thedistal end of the catheter body. The electrode assembly includes aporous electrode arrangement that is generally transverse to thecatheter body. The porous electrode arrangement comprises one or moreelectrodes electrically connected to a suitable energy source and aporous sleeve mounted in surrounding relation to the one or moreelectrodes and defining an open space between the porous sleeve and theone more electrodes. One or more irrigation openings fluidly connect theopen space to a lumen extending through the catheter through which fluidcan pass. In use, fluid passes through the lumen in the catheter,through the one or more irrigation openings, into the open space andthrough the porous sleeve.

In another embodiment, the invention is directed to a cathetercomprising an elongated generally-tubular catheter body having proximaland distal ends. An electrode assembly is provided at the distal end ofthe catheter body. The electrode assembly comprises a non-conductivetubing mounted on the distal end of the catheter body and having a lumenextending therethrough. A generally-straight porous electrode is mountedon the non-conductive tubing and is generally transverse to the axis ofthe catheter body. The porous electrode comprises one or more electrodeselectrically connected to a suitable energy source and a porous sleevemounted in surrounding relation to the one or more electrodes anddefining an open space between the porous sleeve and the one moreelectrodes. One or more irrigation openings fluidly connect the openspace to the lumen extending through the non-conductive tubing.

The invention is also directed to a method for ablating heart tissue.The method comprises inserting the distal end of a catheter as describedabove into the heart of a patient and forming at least one linear lesionin the atrial tissue with the porous electrode by simultaneouslysupplying ablation energy to the one or more electrodes and introducingfluid through the irrigation openings so that the fluid passes throughthe porous sleeve.

In another embodiment, the invention is directed to a method fortreating atrial fibrillation. The method comprises inserting the distalend of a catheter as described above into an atrium of the heart of apatient and forming at least one linear lesion in the atrial tissue withthe porous electrode by simultaneously supplying ablation energy to theone or more electrodes and introducing fluid through the irrigationopenings so that the fluid passes through the porous sleeve.

DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a side cross-sectional view of an embodiment of the catheterof the invention.

FIG. 2 is a side cross-sectional view of a catheter body according tothe invention, including the junction between the proximal shaft anddistal shaft.

FIG. 3 is a side view of an electrode assembly according to theinvention.

FIG. 4 is an end cross-sectional view of the electrode assembly of FIG.3 along line 4-4.

FIG. 5 is a cross sectional view of a portion of the catheterintermediate section showing one means for attaching the puller wire.

FIG. 6 is a top cross sectional views of a preferred puller wire anchor.

FIG. 7 is a side cross sectional views of the puller wire anchor of FIG.6.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a catheter having an irrigated tubular ablationelectrode. As shown in FIG. 1, the catheter comprises an elongatedcatheter body 10 having proximal and distal ends with an electrodeassembly 15 mounted at the distal end of the catheter body and a controlhandle 16 at the proximal end of the catheter body.

With reference to FIG. 2, the catheter body 10 comprises an elongatedtubular construction having a relatively long proximal shaft 12 and arelatively short distal shaft 14. The proximal shaft 12 has a single,axial or central lumen 18. The proximal shaft 12 is flexible, i.e.,bendable, but substantially non-compressible along its length. Theproximal shaft 12 can be of any suitable construction and made of anysuitable material. A presently preferred construction comprises an outerwall 22 made of polyurethane or PEBAX®. The outer wall 22 comprises animbedded braided mesh of stainless steel or the like to increasetorsional stiffness of the proximal shaft 12 so that, when the controlhandle 16 is rotated, the distal shaft 14 will rotate in a correspondingmanner.

The outer diameter of the proximal shaft 12 is not critical, but ispreferably no more than about 8 french, more preferably 7 french.Likewise the thickness of the outer wall 22 is not critical, but is thinenough so that the central lumen 18 can accommodate an infusion tube, apuller wire, lead wires, and any other wires, cables or tubes. Ifdesired, the inner surface of the outer wall 22 is lined with astiffening tube (not shown) to provide improved torsional stability. Inthe depicted embodiment, the distal shaft 14 comprises a short sectionof tubing 19 having three lumens, namely, a lead wire lumen 30, a pullerwire lumen 32, and an infusion lumen 34. The wires and tube aredescribed in more detail below. The tubing 19 is made of a suitablenon-toxic material that is preferably more flexible than the proximalshaft 12. A presently preferred material for the tubing 19 is braidedpolyurethane, i.e., polyurethane with an embedded mesh of braidedstainless steel or the like, that is more flexible than the catheterbody. The number and size of the lumens is not critical and can varydepending on the various wires, tubes and other components carried bythe catheter. In a preferred embodiment, the distal shaft 14 has anouter diameter ranging from about 5 french (0.066 inch) to 8 french(0.105 inch), and the lead wire lumen 30 and puller wire lumen 32 aregenerally about the same size, each having a diameter of from about0.020 inch to about 0.024 inch, preferably 0.022 inch, with the infusionlumen 34 having a slightly larger diameter of from about 0.032 inch toabout 0.038 inch, preferably 0.035 inch.

One means for attaching the proximal shaft 12 to the distal shaft 14 isillustrated in FIG. 2. The proximal end of the distal shaft 14 comprisesan outer circumferential notch 24 that receives the inner surface of theouter wall 22 of the proximal shaft 12. The distal shaft 14 and proximalshaft 12 are attached by glue or the like. Other arrangements forjoining the proximal and distal shafts are considered within the scopeof the invention. For example, the proximal and distal shafts can bemade from a single tubing so that the proximal and distal shafts includethe same number of lumens. Alternatively, if a stiffening tube isprovided, the stiffening tube can extend slightly beyond the distal endof the proximal shaft 12 (e.g., about 3 mm) and be glued to the proximalshaft, with the proximal end of the distal shaft 14 cored out to receivethe distal end of the stiffening tube, creating a lap joint. The lapjoint and the butt joint formed between the distal end of the proximalshaft 12 and the proximal end of the distal shaft 14 can be secured withpolyurethane glue or the like. In another alternative, the proximalshaft 12 can be thermally fused to the distal shaft 14.

If desired, a spacer (not shown) can be located within the proximalshaft 12 at its distal end, adjacent the proximal end of the distalshaft 14. The spacer provides a transition in flexibility at thejunction of the proximal shaft and distal shaft, which allows thisjunction to bend smoothly without folding or kinking. A catheter havingsuch a spacer is described in U.S. Pat. No. 5,964,757, the disclosure ofwhich is incorporated herein by reference.

At the distal end of the distal shaft 14 is a non-retractable electrodeassembly 15, as shown in FIGS. 3 and 4. The electrode assembly 15 hasproximal and distal ends and comprises an elongated non-conductivetubing 37 mounted on the distal end of the distal shaft 14 and anelongated, porous electrode 38 at the distal end of the non-conductivetubing. In the depicted embodiment, the porous electrode 38 is generallystraight and generally transverse to the catheter body 10, andpreferably forms an angle with the axis of the catheter body rangingfrom about 75° to about 110°.

The proximal end of the non-conductive tubing 37 is generally coaxialwith the catheter body 10, and the mid-section of the non-conductivetubing forms a curve that first bends away from and then back toward andpast the axis of the catheter body, with the porous electrode 38 mountedover the straight distal end of the non-conductive tubing, as best shownin FIG. 3. This “foot” or “heel” shape is particularly suitable forablating a linear lesion with the porous electrode 38 due to itsinherent stability. Specifically, it limits the electrode roll whenlongitudinal push forces are applied to the catheter body, particularlywhen the porous electrode is placed against the uneven contours of theheart wall. Thus, when the user exerts a longitudinal force on thecatheter body, the entire length of the porous electrode tends to exerta force on the tissue rather than the proximal end of the porouselectrode being pushed into the tissue and the distal end of the porouselectrode being forced away from the tissue.

The generally straight shape of the porous electrode 38 is particularlysuitable for creating long linear lesions. However, other shapes for theelectrode assembly 15 are also contemplated within the scope of theinvention, such as where the porous electrode 38 is curved or bent. Acurved porous electrode 38 could be used for creating curved lesions forpulmonary vein isolation. Other electrode assembly shapes that can beused for the invention are described in U.S. Pat. No. 6,371,955, thedisclosure of which is incorporated herein by reference.

The non-conductive tubing 37 is generally tubular and includes fourlumens, namely, a lead wire lumen 40, a thermocouple lumen 41, astiffening wire lumen 42 and an irrigation lumen 43. As will becomeapparent, the number and sizes of the lumens in the non-conductivetubing are not critical and can vary depending on the desiredapplication. The non-conductive tubing 37 can be made of any suitablebiocompatible plastic, such as polyurethane or PEBAX®.

The porous electrode 38 comprises one or more electrodes mounted overthe non-conductive tubing 37 and covered by a porous material. In thedepicted embodiment, a single coiled ribbon electrode 44 is mounted insurrounding relating to the non-conductive tubing 37. The ribbonelectrode 44 can be made of any suitable electrically-conductive metalor other material, such as platinum or gold, and can be an alloy, suchas a platinum-iridium alloy. Alternatively, the ribbon electrode 44 canbe replaced with a series of ring electrodes or with a thin metalcoating that is deposited directly onto the non-conductive tubing 37.Other electrode arrangements are contemplated within the scope of theinvention.

The non-conductive tubing includes a series of irrigation openings 39 inthe region of the ribbon electrode 44. In the depicted embodiment, threeirrigation openings 39 are provided between the turns of the ribbonelectrode 44. The irrigation openings 39 fluidly connect the irrigationlumen 43 of the non-conductive tubing 37 to the outside non-conductivetubing. Preferably the irrigation openings 39 are located only on theside of the porous electrode 38 that is to be in contact with the tissueto be ablated, which is typically the side facing away from the catheterbody 10. The irrigation openings 39 can be any suitable shape, such asrectangular or ovular slots or round holes. In an exemplary embodiment,a space of approximately 3.5 mm is provided between the centers of theirrigation openings 39. As would be recognized by one skilled in theart, the precise number, size, shape and arrangement of irrigation ports39 can vary as desired.

A porous sleeve 46 is mounted in surrounding relation to the ribbonelectrode 44. The porous sleeve 46 is made of a material through whichfluid can pass. The proximal and distal ends of the porous sleeve 46extend beyond the proximal and distal ends of the ribbon electrode 44.As discussed further below, the proximal and distal ends of the poroussleeve 46 are sealed over the non-conductive tubing 37 to create an openspace 47 between the porous sleeve and the non-conductive tubing andribbon electrode 44.

With this design, saline or other fluid can pass out through theirrigation openings 39 between the coils of the ribbon electrode 44 intothe open space 47 defined by the porous sleeve 46 and then through theporous sleeve. When radio frequency (RF) energy or other appropriateenergy is supplied to the ribbon electrode 44, the RF current is carriedto cardiac tissue by saline flow through the porous sleeve 46 while theporous sleeve is in contact with the tissue. The RF current resistivelyheats the tissue in contact with the porous sleeve 46, causing permanentcellular necrosis of the tissue, thereby creating a linear lesion. Theporous sleeve 46 allows for the flow of saline around the ribbonelectrode 44 to keep the electrode temperature low during energyapplication.

This design permits safe delivery of higher levels of RF power that arerequired to create lesions deep enough to treat arrhythmias such asatrial fibrillation, atrial flutter and ventricular tachycardia.Although with other irrigated electrode designs it is possible forcoagulum formation and tissue charring to occur due to inefficientirrigation that results in local hot spots at the tissue/electrodeinterface, the porous sleeve electrode design ensures that RF currentcannot be delivered to the tissue without the presence of the coolingsaline or other fluid. Therefore RF lesions can be created only atlocations that are also cooled by the saline irrigation.

As noted above, the porous sleeve 46 is made of a material through whichsaline and other fluid can pass. Preferably the porous sleeve 46 isformed of a generally non-compressible material. As used herein, theterm “non-compressible” means that the material generally does notexhibit appreciable or sufficient compressibility between its inner andouter surfaces to conform to surface irregularities of the tissueagainst which the porous electrode is placed. A particularly suitablematerial for the porous sleeve 46 is expanded polytetrafluoroethylene(ePTFE), although the sleeve can also be made of other porous materials,such as porous polyethylene, porous silicon, porous urethane, porousnylon, sintered ceramics, and tight weaves of dacron and other wovenmeshes. Such porous materials are formed using conventional techniques,such as, for example by blowing the material or by drilling micro holeswithin the material. The porosity of the material desirably rangesbetween about 5 and 50 microns.

In a particularly preferred embodiment, the porous sleeve 46 comprisesePTFE having an inner diameter of 0.080 inch and an outer diameter ofabout 0.096 inch, with the ePTFE being expandable to no more than 10% ata distilled water flow rate of 30 to 40 cc/min. The porous electrodepreferably has a length L ranging from about 10 to about 25 mm, morepreferably from about 10 to about 15 mm, still more preferably about 11mm. In one embodiment, the degree of porosity of the porous sleeve 46over its length is generally uniform. This uniformity coupled with theflow restrictiveness of the material results in the fluid emanating fromthe porous sleeve 46 in a generally even flow over its entire outersurface.

An infusion tube 48 is provided for infusing fluid, such as saline, tothe irrigation openings 39. The infusion tube 48 is preferably made of abiocompatible plastic, such as polyimide. The infusion tube 48 has adistal end anchored in the proximal end of the irrigation lumen 43 ofthe non-conductive tubing 37. The infusion tube 48 extends through theinfusion lumen 34 of the distal shaft 14, through the proximal shaft 12,out the proximal end of the control handle 16, and terminates in a luerhub 49 or the like at a location proximal to the control handle. In analternative arrangement, a single lumen side arm (not shown) is fluidlyconnected to the central lumen 18 near the proximal end of the catheterbody 10, as described in more detail in U.S. Pat. No. 6,120,476, theentire disclosure of which is incorporated herein by reference.Alternatively, the infusion tube 48 can terminate within the distal endof the infusion lumen 34 of the distal shaft 14, with a second infusiontube (not shown) provided that extends from the proximal end of theinfusion lumen, through the proximal shaft 12 and out through thecontrol handle 16. Such a design is also described in more detail inU.S. Pat. No. 6,120,476.

An electrode lead wire 50 is attached to the ribbon electrode 44 forelectrical connection to a suitable connector (not shown), which isattached to a source of ablation energy, such as RF energy (not shown).The electrode lead wire 50 is soldered, welded or otherwise attached tothe ribbon electrode 44. The electrode lead wire 50 can comprise anysuitable material, and is preferably a copper wire or a Monel wire withan appropriate non-conductive covering over most of its length. Theelectrode lead wire 50 for the ribbon electrode 38 extends through thelead wire lumen 40 of the non-conductive tubing 37, the lead wire lumen30 of the distal shaft 14, the central lumen 18 of the proximal shaft12, and the control handle 16, and is connected to a suitable source ofablation energy (not shown) by means of an appropriate connector as isgenerally known in the art.

One or more mapping electrodes are mounted over the non-conductivetubing 37. The mapping electrodes enable the user to perform pacemapping to assess tissue contact as well as electrical conductivitywithin the atrium or other region being treated before and afterablation. In the depicted embodiment two proximal mapping electrodes 52are mounted proximal to the porous electrode 38, and two distal mappingelectrodes 54 are mounted distal to the tubular electrode. Each of theproximal and distal mapping electrodes 52 and 54 comprises a ringelectrode that is mounted in surrounding relation to the non-conductivetubing 37, although other electrode arrangements are considered withinthe scope of the invention. The ring electrodes can be made of anysuitable material, and are preferably made of platinum or an alloy ofplatinum and iridium. An electrode lead wire 50 is welded, soldered orotherwise attached to each of the mapping electrodes 52 and 54. Eachmapping electrode 52 and 54 preferably has a length ranging from about0.5 mm to about 2 mm, more preferably from about 0.5 mm to about 1 mm.The spaces between the mapping electrodes 52 and 54, as well as thespaces between the mapping electrodes and the porous electrode 38,preferably range from about 0.5 mm to about 3 mm, more preferably fromabout 0.5 mm to about 1.5 mm.

To maintain the desired shape of the non-conductive tubing 37 and porouselectrode 38, a stiffening wire 56 is provided within the stiffeningwire lumen 42 of the non-conductive tubing. The stiffening wire 56 ismade of a material having shape-memory, i.e., that can be straightenedor bent out of its original shape upon exertion of a force and iscapable of substantially returning to its original shape upon removal ofthe force. A particularly preferred material for the stiffening wire isa nickel/titanium alloy. Such alloys typically comprise about 55% nickeland 45% titanium, but may comprise from about 54% to about 57% nickelwith the balance being titanium. A preferred nickel/titanium alloy isnitinol, which has excellent shape memory, together with ductility,strength, corrosion resistance, electrical resistivity and temperaturestability. The stiffening wire 56 can have any desired cross-sectionalarea and need not be circular. The stiffening wire 56 can be pre-shapedto the desired shape using a heat-treating process, as is generallyknown in the art. Alternatively, the stiffening wire 56 can beeliminated, and the non-conductive tubing can be pre-shaped in thedesired configuration.

Additionally, one or more temperature sensing means can be provided formeasuring the electrode/tissue interface temperatures near the porouselectrode 38 during ablation. Any conventional temperature sensingmeans, e.g., a thermocouple or thermistor, may be used. In the depictedembodiment, two thermocouples 70 and 72 are provided. Specifically, adistal thermocouple 70 is provided distal to the porous electrode 38,and a proximal thermocouple 72 is provided proximal to the porouselectrode, as described in more detail below. As would be recognized byone skilled in the art, other temperature sensing designs can be used,or the temperature sensors can be eliminated altogether.

To make the electrode assembly 15 described above, an appropriate lengthof an ePTFE sleeve (for example, around 15 mm) is cut, and five holesare drilled about 1 mm from each end of the ePTFE sleeve evenly aboutits circumference. A stainless steel mandrel having a Teflon tubingmounted over it is introduced through the ePTFE sleeve. Polyurethaneglue is applied to one end of the ePTFE sleeve to form a 1 mm band, anda small rubber O-ring is slid over the band of polyurethane glue tocompress the end of the ePTFE sleeve onto the Teflon over the mandrel.Once the polyurethane glue has cured, the O-ring, Teflon and mandrel areremoved. V-shaped notches are cut into each end of the ePTFE sleeve.

The ribbon electrode 44 is formed by wrapping a platinum ribbon around a0.065 inch gauge pin about 10 times, with no gaps between the turns ofthe coil. The coil is removed from the pin, and the remaining, uncoiledplatinum ribbon is cut off from the coil. Platinum rings are welded tothe ends of the wound coil.

The non-conductive tubing 37 is cut to an appropriate length, forexample, about 40 mm. The three irrigation openings 39 are drilled intothe irrigation lumen 43 of the non-conductive tubing 37 at locations 11mm, 14.5 mm and 18 mm from what is to be the distal end of thenon-conductive tubing. The proximal end of the irrigation lumen 43 istrepanned to expand the lumen so that the infusion tube 48 will fitabout 2 mm into the irrigation lumen.

Three electrode lead wires 50, two for the proximal ring electrodes 52and one for the ribbon electrode 44, are introduced into the lead wirelumen 40 of the non-conductive tubing 37. Five lead wire access holesare punched into the non-conductive tubing 37 using a needle, with twopositioned about 7 to 8 mm from the distal end of the non-conductivetubing and three positioned about 20 to 22 mm from the distal end of thenon-conductive tubing. The three lead wires 50 are pulled out of thethree more proximal holes, and the insulation is removed from the tipsof the lead wires. Two of the electrode lead wires 50 are welded to twoplatinum rings to form the proximal ring electrodes 52. The thirdelectrode lead wire 50 is welded to what is to be the proximal end ofthe platinum coil that forms the ribbon electrode 44. The two platinumrings are than loaded over the non-conductive tubing 37 and aligned withthe two most proximal punched holes. The platinum coil is loaded overthe non-conductive tubing 37 and aligned with the third most proximalpunched hole. The coil is adjusted so that the turns are evenly spacedwith the three irrigation openings 39 positioned between the turns, andthe platinum coil is anchored in place by applying polyurethane glue tothe proximal and distal ends of the ribbon electrode 44.

Two thermocouple wire holes are punched into the thermocouple lumen 41of the non-conductive tubing 37 approximately 10 mm and 19 mm from thedistal end of the non-conductive tubing, i.e., as positions justproximal and distal to the ribbon electrode 44. Two thermocouple wirepairs, such as a constantan wire and a copper wire, are introduced intothe thermocouple lumen 41 and pulled through the thermocouple wireholes. The insulation is scraped from the distal ends of thethermocouple wires and the two wires of each pair are soldered togetherat their distal ends. A short piece of insulating polyimide tubing 74 isinserted over the distal end of each thermocouple wire pair, held inplace with polyurethane glue, and cut to a length of about 0.75 mm. Thedistal ends of the thermocouples 70 and 72 are wrapped around theoutside of the non-conductive tubing 37 and glued in place.

The ePTFE sleeve, prepared as described above, is loaded over theplatinum coil, which is mounted over the non-conductive tubing 37. TheV-shaped notches in the ePTFE sleeve are aligned with the punched holesfor the electrode lead wires 50. Two additional electrode lead wires 50are introduced into the lead wire lumen 40 of the non-conductive tubing37, pulled out through the two most distal punched holes, and welded tothe undersides of two platinum rings to form the two distal mappingelectrodes 54. A 1 mm wide band of polyurethane glue is applied to thenon-conductive tubing 37 about 22 mm from its distal end. The ePTFEsleeve is slid under the two proximal mapping electrodes 52 and over theband of glue, with the lead wires being aligned in the V-shaped notch inthe proximal end of the ePTFE sleeve. Additional polyurethane glue isapplied around the proximal end of the ePTFE sleeve. Another 1 mm wideband of polyurethane glue is applied over the non-conductive tubingabout 7 mm from its distal end. Nylon thread is wrapped around thedistal end of the ePTFE sleeve to adhere the ePTFE sleeve to the secondglue band. The nylon thread is removed, and the two distal mappingelectrodes 54 are slid over the distal end of the ePTFE sleeve.Additional polyurethane glue is applied over the distal end of the ePTFEsleeve.

A 0.019 inch pre-shaped Nitinol stiffening wire 56 is introduced intothe stiffening wire lumen 42 of the non-conductive tubing 37, and theNitinol wire is cut flush with the proximal end of the non-conductivetubing. The infusion tube 48 is loaded into the trepanned (proximal) endof the irrigation lumen 43 of the non-conductive tubing 37. Polyurethaneglue is applied to the proximal end of the non-conductive tubing 37 toseal all lumens except for the irrigation lumen 43, thereby bonding theinfusion tube 47 in place. If desired, a plastic blocker can be insertedinto the irrigation lumen 43 during manufacturing to prevent glue fromentering into the irrigation lumen.

The distal end of the non-conductive tubing 37 is cut a distance ofabout 0.5 mm to about 1 mm from the most distal mapping electrode 54.Polyurethane glue is applied to the distal end of the non-conductivetubing 37, with some of the glue being allowed to migrate a shortdistance into the distal end of the lumens in the non-conductive tubing.After curing for about an hour, additional polyurethane glue is added tobuild up a ball tip 58 at the distal end of the non-conductive tubing37, thereby forming an atraumatic tip. As would be recognized by oneskilled in the art, other atraumatic tips could be used, such as thosedescribed in U.S. patent application Ser. No. 09/551,467, entitled“Catheter Having Mapping Assembly,” the disclosure of which isincorporated herein by reference.

All of the electrode lead wires 50 and thermocouple wires 70 and 72extend through the lead wire lumen 30 in the distal shaft 14. Within theproximal shaft 12, the wires extend through a protective tubing 36 tokeep the wires from contacting other components extending through thecentral lumen 18. The protective tubing 36 is preferably anchored at itsdistal end to the proximal end of the distal shaft 14 by gluing it inthe lead wire lumen 30 with polyurethane glue or the like. The electrodelead wires 50 then extend out through the control handle 16 and to asuitable monitoring device or source of ablation energy (not shown), asappropriate, via a suitable connector 60, as is generally known in theart. The thermocouple wires 70 and 72 similarly extend out through thecontrol handle 16 and to a connector 62 connectable to a temperaturemonitor (not shown).

A puller wire 84 is provided for deflection of the distal shaft 14. Thepuller wire 84 extends through the proximal shaft 12, is anchored at itsproximal end to the control handle 16, and is anchored at its distal endto the distal shaft 14. The puller wire 84 is made of any suitablemetal, such as stainless steel or Nitinol, and is preferably coated withTeflon® or the like. The coating imparts lubricity to the puller wire84.

A compression coil 86 is situated within the proximal shaft 12 insurrounding relation to the puller wire 84. The compression coil 86extends from the proximal end of the proximal shaft 12 to the proximalend of the distal shaft 14. The compression coil 86 is made of anysuitable metal, preferably stainless steel. The compression coil 86 istightly wound on itself to provide flexibility, i.e., bending, but toresist compression. The inner diameter of the compression coil 86 ispreferably slightly larger than the diameter of the puller wire 84. TheTeflon® coating on the puller wire 84 allows it to slide freely withinthe compression coil 86. If desired, particularly if the lead wires 50are not enclosed by a protective tubing 36, the outer surface of thecompression coil 86 is covered by a flexible, non-conductive sheath 88,e.g., made of polyimide tubing, to prevent contact between thecompression coil and any other wires within the proximal shaft 12.

The compression coil 86 is anchored at its proximal end to the outerwall 22 of the proximal shaft 12 by proximal glue joint 90 and at itsdistal end to the distal shaft 14 by distal glue joint 92. Both gluejoints 90 and 92 preferably comprise polyurethane glue or the like. Theglue may be applied by means of a syringe or the like through a holemade between the outer surface of the proximal shaft 12 and the centrallumen 18. Such a hole may be formed, for example, by a needle or thelike that punctures the outer wall 22 of the proximal shaft 12 that isheated sufficiently to form a permanent hole. The glue is thenintroduced through the hole to the outer surface of the compression coil86 and wicks around the outer circumference to form a glue joint aboutthe entire circumference of the compression coil 86.

The puller wire 84 extends into the puller wire lumen 32 of the distalshaft 14. Preferably the puller wire 84 is anchored at its distal end tothe side of the shaft 14, as shown in FIGS. 5 to 7. A T-shaped anchor 98is formed which comprises a short piece of tubular stainless steel 100,e.g., hypodermic stock, which is fitted over the distal end of thepuller wire 84 and crimped to fixedly secure it to the puller wire. Thedistal end of the tubular stainless steel 100 is fixedly attached, e.g.,by welding, to a stainless steel cross-piece 102 such as stainless steelribbon or the like. The cross-piece 102 sits in a notch 104 in a wall ofthe flexible tubing 19 that extends into the puller wire lumen 32 of thedistal shaft 14. The stainless steel cross-piece 102 is larger than theopening and, therefore, cannot be pulled through the opening. Theportion of the notch 104 not filled by the cross-piece 102 is filledwith glue 106 or the like, preferably a polyurethane glue, which isharder than the material of the flexible tubing 19. Rough edges, if any,of the cross-piece 102 are polished to provide a smooth, continuoussurface with the outer surface of the flexible tubing 19. Within thepuller wire lumen 32 of the distal shaft 14, the puller wire 84 extendsthrough a plastic, preferably Teflon®, puller wire sheath 94, whichprevents the puller wire 84 from cutting into the wall of the distalshaft 14 when the distal shaft is deflected. Any other suitabletechnique for anchoring the puller wire 84 in the distal shaft 14 canalso be used.

Longitudinal movement of the puller wire 84 relative to the proximalshaft 12, which results in deflection of the distal shaft 14, isaccomplished by suitable manipulation of the control handle 16. Examplesof suitable control handles for use in the present invention aredisclosed, for example, in U.S. Pat. Nos. Re 34,502 and 5,897,529, theentire disclosures of which are incorporated herein by reference.

In use, a suitable guiding sheath is inserted into the patient. Anexample of a suitable guiding sheath for use in connection with thepresent invention is the Preface™ Braiding Guiding Sheath, commerciallyavailable from Biosense Webster (Diamond Bar, California). The distalend of the sheath is guided into one of the atria. A catheter inaccordance with the present invention is fed through the guiding sheathuntil its distal end extends out of the distal end of the guidingsheath. As the catheter is fed through the guiding sheath, the electrodeassembly can be straightened to fit through the sheath, and it willreturn to its original shape upon removal of the sheath.

The proximal and/or distal mapping electrodes are then used to measureelectrical activity in the region to be ablated. The porous electrode isused to ablate one or more continuous linear lesions by supplying theribbon electrode with radio frequency energy or other ablation energyand simultaneously introducing fluid through the irrigation openings,into the open space and through the porous sleeve. As used herein, theterminology “linear lesion” refers to any lesion, whether curved orstraight, between two anatomical structures in the heart that issufficient to block a wavelet, i.e., forms a boundary for the wavelet.Anatomical structures, referred to as “atrial trigger spots”, are thoseregions in the heart having limited or no electrical conductivity andare described in Haissaguerre et al., “Spontaneous Initiation of AtrialFibrillation by Ectopic Beats Originating in the Pulmonary Veins”, NewEngland Journal of Medicine, 339:659-666 (Sep. 3, 1998), the disclosureof which is incorporated herein by reference. The linear lesionstypically have a length of from about 1 cm to about 6 cm, but can belonger or shorter as necessary for a particular procedure. Thethermocouples or other temperature sensing means can be used to monitorthe temperature of the tissue during ablation. The mapping, ablation andtemperature measuring steps can be performed in any desired order. Inone particular embodiment, the porous electrode is used to isolate thepulmonary vein by creating one or more lesions around the pulmonaryvein.

In an alternative embodiment, the electrode assembly further includes alocation sensor (not shown) for providing location information about theelectrode assembly. Such a design is disclosed in U.S. patentapplication Ser. No. 10/199,525, entitled “Atrial Ablation Catheter andMethod for Treating Atrial Fibrillation,” the disclosure of which isincorporated herein by reference. Preferably the location sensorcomprises a magnetic-field-responsive coil, as described in U.S. Pat.No. 5,391,199, or a plurality of such coils, as described inInternational Publication WO 96/05758. The plurality of coils enablessix-dimensional position and orientation coordinates to be determined.Alternatively, any suitable position sensor known in the art may beused, such as electrical, magnetic or acoustic sensors. Suitablelocation sensors for use with the present invention are also described,for example, in U.S. Pat. Nos. 5,558,091, 5,443,489, 5,480,422,5,546,951, and 5,568,809, and International Publication Nos. WO95/02995, WO 97/24983, and WO 98/29033, the disclosures of which areincorporated herein by reference.

If desired, two or more puller wires can be provided to enhance theability to manipulate the intermediate section. In such an embodiment, asecond puller wire and a surrounding second compression coil extendthrough the proximal shaft and into an additional off-axis lumen in thedistal shaft. The first puller wire can be anchored proximal to theanchor location of the second puller wire. Suitable designs of cathetershaving two or more puller wires, including suitable control handles forsuch embodiments, are described, for example, in U.S. Pat. Nos.6,123,699, 6,171,277, 6,183,435, 6,183,463, 6,198,974, 6,210,407, and6,267,746, the disclosures of which are incorporated herein byreference.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention.

Accordingly, the foregoing description should not be read as pertainingonly to the precise structures described and illustrated in theaccompanying drawings, but rather should be read consistent with and assupport to the following claims which are to have their fullest and fairscope.

1. A method for ablating heart tissue comprising: inserting into theheart of a patient the distal end of a catheter comprising: an elongatedgenerally-tubular catheter body having proximal and distal ends; and anelectrode assembly at the distal end of the catheter body, the electrodeassembly including a porous electrode arrangement that is generallytransverse to the catheter body, the porous electrode arrangementcomprising: one or more electrodes electrically connected to a suitableenergy source; a porous sleeve mounted in surrounding relation to theone or more electrodes and defining an open space between the poroussleeve and the one or more electrodes; and one or more irrigationopenings fluidly connecting the open space to a lumen extending throughthe catheter through which fluid can pass; wherein, in use, fluid passesthrough the lumen in the catheter, through the one or more irrigationopenings, into the open space and through the porous sleeve; and formingat least one linear lesion in the atrial tissue with the porouselectrode by simultaneously supplying ablation energy to the one or moreelectrodes and introducing fluid through the irrigation openings so thatthe fluid passes through the porous sleeve.
 2. A method for treatingatrial fibrillation comprising: inserting into the heart of a patientthe distal end of a catheter comprising: an elongated generally-tubularcatheter body having proximal and distal ends; and an electrode assemblyat the distal end of the catheter body, the electrode assembly includinga porous electrode arrangement that is generally transverse to thecatheter body, the porous electrode arrangement comprising: one or moreelectrodes electrically connected to a suitable energy source; a poroussleeve mounted in surrounding relation to the one or more electrodes anddefining an open space between the porous sleeve and the one or moreelectrodes; and one or more irrigation openings fluidly connecting theopen space to a lumen extending through the catheter through which fluidcan pass; wherein, in use, fluid passes through the lumen in thecatheter, through the one or more irrigation openings, into the openspace and through the porous sleeve; and forming at least one linearlesion in the atrial tissue with the porous electrode by simultaneouslysupplying ablation energy to the one or more electrodes and introducingfluid through the irrigation openings so that the fluid passes throughthe porous sleeve.